1. Field of the Invention
This invention concerns automatic testing devices and more particularly devices for automatically checking proper completion of the machining of threaded features in a workpiece by a multimode testing device.
2. Description of the Prior Art
In automatic multistage machining of workpieces with equipment such as transfer lines, it is common for threaded features such as bores and studs to be formed in or on the workpiece.
In such automatic machinery, it is desirable to monitor the condition of each workpiece to insure that each operation has been satisfactorily completed, such as the proper drilling and tapping of each hole machined into the workpiece.
Typically a large number of threaded holes must be machined into the workpiece in close proximity to each other.
In U.S. Pat. No. 4,437,335, assigned to the same assignee as the present application, there is disclosed a multifunction threaded bore testing device utilizing a probe which is caused to enter the hole, and then pivoted to bring an air outlet in the probe tip into engagement with the bore surface.
Detection of an increased pressure upstream from the air outlet when threads are absent from the bore enables detection of an unthreaded condition of the bore surface.
In the aforementioned patent, the probe tip is tilted by means of a transversely aligned air cylinder to bring the probe into contact with the bore wall. A limit switch detects overtravel which could occur if the part or probe tip was missing. The use of a limit switch does not allow for more refined fault detection, such as out of tolerance sizing of the threaded feature.
While this device has been successfully employed, it does require a sufficient width of the housing to accommodate the transverse air cylinder and the limit switch employed to detect probe overtravel.
It has often been the practice that a number of the individual probes will be stacked together at a single station to simultaneously test a number of holes in a workpiece, and in such situations the housing width should desirably be minimized.
Furthermore, the making of electrical and air supply connections is not convenient in the arrangement shown in U.S. Pat. No. 4,437,335, since the fittings therefor are located on the side of the housing at spaced locations.
Another problem is encountered in accurately aligning the detectors, since each must be adjusted to be accurately aligned with the bore to be tested.
In the aforementioned patent, each testing unit is separately mounted to extend from a mounting plate, and each is adjusted to be accurately located with respect to the bore location during testing. This involves considerable set up time initially, and also when a unit is replaced after servicing.
It has been heretofore known to provide a burst of air to blow out chips from the bore prior to the test, but this has been done at relatively high pressure, and this requires valved control of the blowout air pressure, increasing the complexity of the device.
Accordingly it is an object of the present invention to provide an improved multimode threaded feature testing device having a tilted probe tip with an overtravel test feature while maintaining a narrow width device.
It is yet another object of the present invention to provide a highly accurate overtravel detection mode, which may detect over or under size conditions of the threaded feature.
It is also an object of the present invention to provide an air blowout feature in such a testing device which does not require separate control valving.
It is another object of the present invention to provide a simplified mounting arrangement for accurately aligning the devices with the bores to be tested, and rear located air and electrical connections.